The population in the United States continues to become more diverse each year. Our education system is not designed to support students that do not have English as a first language. The population of multilingual learners are falling behind their English Proficient peers. Inadequate teacher training and program design are contributing factors as to why multilingual learners are not demonstrating an appropriate rate of academic growth each year. This improvement science study was designed to determine a method that would decrease the achievement gap between multilingual learners and English proficient student groups. The teachers and I studied different co-teaching models and determined the best model of implementation for the study. The continuous cycle of improvement provided avenues for the teachers and I to refine the intervention. The study took place from August 2023 to May 2024 in a third-grade classroom in a South Carolina elementary school. The data was collected through interviews, observations, and student achievement data. The findings in this study evaluated the co-teaching model and determined that this intervention was a contributing factor in strengthening instructional practices and developed a sustainable model that could be replicated and implemented for multilingual learners as a means to improve the overall education system. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]